1. Field of the Invention
The present invention relates to an optical-path switching apparatus, an optical-device switching apparatus for an optical microscope and a locking apparatus for use in transporting an optical microscope. More particularly, the present invention relates to an optical-path switching apparatus for an optical microscope permitting selection of observation from naked-eye observation through an ocular lens, observation through a TV camera and the like, an optical-device switching apparatus and a locking apparatus for use in transporting an optical microscope.
2. Description of the Related Art
In recent years, lens tubes of a type having a TV optical path have been disclosed which permit a variety of TV cameras to be attached, as well as permitting a naked-eye observation to be performed and a photographing lens to be attached. For example, an optical system for a microscope permitting both naked-eye observation and TV camera observation to be performed has been disclosed, wherein the TV camera has a function to serve as a finder when a photographing operation is performed.
FIG. 1 is a diagram showing the prior art optical system.
The prior art optical system shown in FIG. 1 has a deflection prism 22 for directly introducing light, reflected by or through a specimen S placed on a stage 20 and allowed to pass through an objective lens 21, into ocular lenses 33a and 33b; a plurality of reflecting members 23 to 27 for receiving the light beam from the objective lens 21, and which are disposed to form a loop optical path when the deflection prism 22 is positioned on the outside of the optical path; relay lenses 28 and 29 disposed in the foregoing loop optical path; and a reflecting member or a beam splitter 31 which is allowed to be inserted into a position more rearwards than secondary image-formation position I.sub.2 in the loop optical path.
Moreover, the foregoing prior art optical system has a reflecting member 41 for directing the light beam from a position more rearwards than the first image-formation position I.sub.1 in the loop optical path to a photographing optical path; reflecting surfaces 34 and 35 for introducing light beams branched by the reflecting member or the beam splitter 31 to the ocular lenses 33a and 33b through a prism 32; a photographing camera 42 disposed on the photographing optical path; and a TV camera 45 disposed on an injection optical path from the loop optical path.
When the following optical devices at three switching positions are inserted or removed with a relation among the following devices being maintained: the deflection prism 22, the reflecting mirror or the reflecting members 23 among the plural reflecting surfaces 23 to 27, which is a reflecting member forming a first reflecting surface, and the reflecting member or the beam splitter 31 positioned more rearwards than the secondary image-formation position I.sub.2 in the loop optical path, naked-eye observation, photographing and TV observation can be performed as required. That is, when photographing is performed, either of the naked-eye observation or the TV observation can be selected as the function of a finder.
When the prism 23 has been brought to the outside of the optical path, a correction prism 23A is inserted in place of the prism 23. Thus, light from the objective lens 21 is introduced into the TV camera 45. Note that light allowed to pass through the reflecting member 24 is used to perform a photometry operation and the like.
Since the operation of the microscope having the foregoing multi-functions is complicated, there arises an important requirement for forming the portions for operating the switching positions into electric structures so as to automate all of the sequential operations required to perform a predetermined observation in order to easily operate the optical microscope.
In a case where the microscope disclosed in Japanese Patent Application No. H6-203626 and capable of using all of naked-eye observation, photographing and TV observation is intended to have a structure such that the observation states can electrically be switched, there is the necessity that the following portions are related to one another when electrically operated: a first optical device-switching portion including the deflection prism; a second optical-device switching portion including a reflecting mirror or a prism forming a first reflecting surface among a plurality of reflecting surfaces; and a third optical-device switching portion including the reflecting member or the beam splitter positioned more rearwards than the secondary image-formation position I.sub.2 in the loop optical path.
As shown in FIG. 2 which is a control block diagram of the prior art optical-path switching apparatus for an optical microscope, a method for realizing the foregoing structure must comprise operation circuits, actuators, detection circuits, which are disposed corresponding to each switching portion, and a control unit for controlling the foregoing elements while relating the same to one another.
FIG. 3 is a cross sectional view of the optical-device switching apparatus for electrically inserting and removing, with respect to an optical path, optical devices, such as prisms and reflecting mirrors to be used at the switching positions.
Referring to FIG. 3, reference numerals 51a and 51b represent prisms respectively having different functions, and 52 represents a prism holding member for holding the prisms 51a and 51b. Reference numeral 53 represents a guide rod having a click groove for supporting the prism holding member 52, the click groove being arranged to receive a fixing member (not shown) secured to the prism holding member 52. Reference numeral 54 represents a sub guide rod for, together with the guide rod 53, supporting the prism holding member 52.
Reference numeral 55 represents a motor, 56 represents a deceleration mechanism for decelerating rotation of the motor 55, 57 represents a pinion gear and 58 represents rack secured to the prism holding member 52 and arranged to be engaged to the pinion gear 57. Reference numeral 59 represents a slit plate secured to the prism holding member 52. Reference numeral 60 represents a sensor for detecting insertion and removal of the slit plate 59. Reference numeral 61 represents a body for supporting the foregoing guide rod 53, the sub guide rod 54, the motor 55, the pinion gear 57 and the sensor 60.
In the optical-path switching apparatus having the foregoing structure, the sensor 60 detects insertion or removal of the slit plate 59 so that rotation of the motor 55 is interrupted. Simultaneously, the fixing member is received in the click groove. Thus, the optical devices are switched with respect to the optical path and positioned at predetermined positions.
Another optical-path switching apparatus for an optical microscope having a structure as shown in FIG. 4 has been known in Japanese Patent Application KOKAI Publication No. S56-36614.
Referring to FIG. 4, reference numerals 71a, 71b and 71c represent magnifying-power changing lenses, 72 represents a turret plate disposed rotatively around a central axis of the apparatus. The lenses 71a, 71b and 71c are attached to the turret plate 72.
Reference numeral 73 represents a slit plate formed individually from the turret plate 72 and disposed in such a manner that the slit plate 73 can be rotated coaxially with the turret plate 72. The slit plate 73 has, on the outer periphery thereof, a thread portion 73a arranged to be engaged to a pinion 75 of a drive motor 74.
Reference numeral 76 represents a linkage pin secured to the turret plate 72, the linkage pin 76 being received in a cut portion 73b formed in the slit plate 73 so as to be capable of moving within a certain range in the cut portion 73b.
Reference numeral 77 represents a photosensor for detecting slits 73c formed in a flange portion of the slit plate 73 to correspond to magnifying-power changing lenses 71a, 71b and 71c, the photosensor 77 being disposed and secured to detect respective slits immediately before the lenses corresponding to the slits 73c reach predetermined positions.
Reference numeral 78 represents a fixing member arranged to be received in a V-groove 72a formed in the outer periphery of the turret plate 72 to correspond to each power-magnifying lens. The fixing member 78 is urged toward inside of the apparatus by a spring and disposed such that when the rotation of the turret plate 72 is stopped at a position at which the fixing member 78 can be received in the V-groove 72a, the lens corresponding to the V-groove 72a can accurately be positioned at a predetermined position.
Therefore, when the drive motor 74 has been rotated in response to a power-magnifying instruction signal, the slit plate 73 is rotated, the rotation being transmitted to the turret plate 72. When the photosensor 77 has detected a predetermined slit 73c, the rotation of the drive motor 74 is interrupted. Although also the rotation of the slit plate 73 is interrupted simultaneously, the structure of the turret plate 72, permitted to be moved within a certain range, causes the slit plate 73 to continue rotation within the range due to inertia.
When the fixing member 78 has been received in the V-groove 72a, the turret plate 72 is accurately stopped at a predetermined position.
However, to operate the three optical-device switching portions while relating the same in the optical system shown in FIG. 1, plural actuators, operation circuits and detection circuits of the same type are required by the number corresponding to the number of the optical-device switching portions shown in FIG. 2. As a result, there arise problems in that the foregoing elements cannot easily be controlled and that the cost cannot be reduced.
Also a plurality of drive mechanisms are required to correspond to the number of the optical-device switching portions, thus resulting in a problem to arise in that the size of the apparatus being enlarged excessively.
In the case where the optical-device switching portions are formed into electric structures by using the optical-path switching apparatus having a structure as shown in FIG. 3, the rotation of the motor 55 is, through the deceleration mechanism 56, directly transmitted to the prism holding member 52 for holding the prisms 51a and 51b.
Therefore, the distance from the fixing member for stopping the prism holding member 52 at a predetermined position in the optical path to the slit plate 59 to be detected by the sensor 60 is required to accurately be adjusted to stop the prism holding member 52 at a predetermined position by stopping the motor 55 at a predetermined position. Thus, there arises a problem in that adjustment cannot easily be performed.
The magnifying power switching apparatus for an optical microscope shown in FIG. 4 has the structure such that the inertia of weights of a turret plate 72 and magnifying power changing lenses 71a to 71c causes rotation to be performed in a period from detection of a slit 73c formed in a slit plate 73 by a photosensor 77 to fixing of an fixing member 78 into a V-groove 72a formed in the outer portion of the turret plate 72.
However, since the inertia force becomes different due to the weights of the magnifying power changing lenses 71a to 71c, a similar difficulty arises in adjusting the positions of the photosensor 77, the slit plate 73 and the V-groove 72a formed on the outer portion of the turret plate 72.
Although the conventional switching mechanism comprises the mechanical portion having durability against load which is determined in consideration of loads which can be applied at the actual use, loads to be applied in the cases except the actual use, that is, loads to be applied during carrying and transportation of the apparatus have not been considered.
If a mechanism of the foregoing type is intended such that a plurality of switching portions are mechanically connected to one another and driven by one motor, increase in the number of prisms enlarges the weight of the portion to be driven. Therefore, if the apparatus is impacted excessively during carrying or transportation, there arises a risk that the mechanical portion is broken or the accuracy deteriorates.
Since optical devices in an optical unit are accurately adjusted in general, adjustments of the portions in which the optical devices are moved usually are complicated considerably.
An optical-path switching apparatus of a type for electrically switching optical devices thereof is required to have excellent accuracy and reduced load. If the load is reduced, the apparatus can easily be affected from external factors. Thus, there arises a problem in that the movable portions are broken or shifted undesirably due to vibrations or impacts occurring during transportation or the like and, therefore, a required function cannot be obtained.
To prevent the foregoing problems, there has been disclosed a transportation locking apparatus for an optical microscope having a structure as shown in FIG. 5 in which elastic members 84 made of sponge or urethane are inserted between an optical device holding member 82, to which optical devices 81, such as prisms, are secured, and two walls of the casing 83 of the apparatus in such a manner that the elastic members 84 are somewhat compressed so as to absorb external force.
Referring to FIG. 5, reference numeral 86 represents a vertical groove formed in the optical device holding member 82. A rotational force of a motor 87 is transmitted, to the groove 86, through a gear 88 and a cam 89 connected by a worm gear, an arm 90 and a bearing 91. Thus, the arm 90 is rotated around a supporting point 92 so that the optical device holding member 82 is moved.
Although the foregoing method is adaptable to apparatuses of a type in which the movable portion can easily be exposed by opening the cover, a multiplicity of mechanical portions must be decomposed to expose the movable portion because a major portion of optical units has complicated internal mechanisms.
If the foregoing portion has been optically adjusted, the foregoing method cannot be employed in actual practice. The reason for this is that a user is required to remove the elastic members when the apparatus is used, and the user cannot assemble and optically adjust the apparatus.
The foregoing method has another problem in that the optical performance deteriorates due to dusts produced from the elastic members. In general, the inside portion of the optical unit usually is formed into a dust-proofing structure to prevent introduction of dusts. The reason for this is that dusts deteriorate the optical performance of the apparatus. Therefore, use of the elastic members made of sponge or urethane deteriorates the effect of the employed dust-proofing structure.
Another method has been disclosed in which the optical device holding member 82 is directly screw-fixed to an arbitrary surface which is in contact with the optical device holding member 82.
The movable portion of the switching apparatus is usually arranged to be in contact with the external member only on a line or at a point in order to reduce the load. Therefore, foregoing method encounters a problem in that the structure becomes too complicated because a cylindrical member 95 having a flange is, as shown in FIG. 6, inserted into the inside portion of the apparatus to be brought into contact with the bottom surface of the optical device holding member 82 so as to be secured to a casing 83 of the optical unit with screws 96 and then a fixing screw 97 is threaded in a thread hole formed in the optical device holding member 82.
In the case where the foregoing securing method is employed, another problem arises in that the optical device holding member 82 can be deformed when the fixing screw 97 is threaded in if each of the bottom surface of the optical device holding member 82, that of the casing and the member 95 are manufactured accurately.
When the optical device holding member 82 in a state where it is floated in the air is pulled by the screw so as to secure the optical device holding member 82, excessive loads act on the optical device holding member 82 and a guide rod for the optical device holding member 82. In the foregoing case, strain and deformation will take place and, therefore, the optical performance deteriorates.
To secure the optical device holding member 82 by forming a portion which is in contact with the optical device holding member 82 on the surface thereof, a method may be employed in which the apparatus is decomposed and the portion is fixed in the inside portion of the apparatus with screws or another method may be employed in which a member having a movable surface is, from outside, brought into contact with the optical device holding member 82 only when the member is secured. However, the former method cannot be employed in practical and the latter method has a problem in that the mechanism is too complicated and the surface, which is brought into contact with the optical device holding member 82, is moved and, therefore, the member cannot stably be brought into contact with the optical device holding member 82 with a required accuracy.